The taxonomy of the genus has been debated, but recent work supports the use of the name Lontra rather than Lutra for New World river otters (Lariviere and Walton 1998, Wozencraft 1993). The following subspecies have been identified L. longicaudis annectens, L. l. colombiana, L. l. enudris, L. l. incarum, L. l. longicaudis and L. l. platensis.

Justification:
This species is considered to be Data Deficient due to ongoing uncertainties about effects of numerous and diverse anthropogenic threats across its range on rates of population decline. The species has an apparent wide distribution along the original range, but there are no systematic studies to evaluate the size of populations and there is no standardized information about changes in the extent of occurrence or area of occupancy. Threats include deforestation, contamination and pollution of aquatic systems, hunting, agricultural activities, mining and damming. However there is no information about population size, number of mature animals or the cumulative effect of threats across the range of the species. This species is suspected to be threatened and further research is needed to inform rates of decline so that it can be assessed against the threatened categories.

Lontra longicaudis occurs from northwestern Mexico south to Uruguay (Gallo 1991), Paraguay, and across the northern part of Argentina to Buenos Aires province (Chehebar 1990; Cockrum 1964; Redford and Eisenberg 1992). It is widespread in the northern and central parts of Argentina (Bertonatti and Parera 1994).

The Neotropical river otter lives in variety of habitats including natural systems such as deciduous and evergreen forests, warm and cool climate rainforests, and coastal savanna swamps (Emmons 1990). Habitat requirements include ample riparian vegetation (Bertonatti and Parera 1994; Redford and Eisenberg 1992), and abundant potential den sites (Soldateli and Blacher 1996). It favours clear, fast-flowing rivers and streams, and may be rare or absent from sluggish, silt-laden lowland rivers. It occurs mostly from 300 to 1,500 m of altitude, but has been found up to 3,000 m (Eisenberg 1989; Emmans 1990; Melendres 1978; Redford and Eisenberg 1992) and in Costa Rica and Uruguay it occurs below 300 m. The greatest abundances of Neotropical otters are in areas with extensive aquatic networks, low chemical and organic pollution, and low human density (Bardier 1992; Blacher 1987). However, this is a versatile species that tolerates environmental modifications well, and has been found occupying areas close to human activity such as irrigation ditches, rice fields and sugar cane plantations (Bertonatti and Parera 1994; Macdonald and Mason 1992).

It feeds mainly on fish, with crustaceans and mollusks contributing to large portions of diet in some areas (Bardier 1992; Bertonatti and Parera 1994; Gallo 1986; Helder-Jose and Ker De Andrade 1997; Passamani and Camargo 1995; Soldateli and Blacher 1996). Fish consumed are mostly from the families Cichlidae, Anostomidae, Characidae, and Pimelodidae (Passamani and Camargo 1995; Spinola and Vaughan 1995). Small mammals, birds, reptiles, and insects are consumed opportunistically (Bertonatti and Parera 1994; Parera 1993; Passamani and Camargo 1995).

It may compete with sympatric Pteronura brasiliensis, however, competition effects may be buffered by use of different habitat, denning sites, size of prey, and by the more crepuscular habits of L. longicaudis (Carter and Rosas 1997; Duplaix 1978). Known predators include anacondas (Eunectes) and jaguars (Panthera onca) (Duplaix 1978; Parera, 1996a), but caimans (Caiman), dogs, and birds of prey may also prey on neotropical otters (Dunstone and Strachan 1988; Parera 1996b).

Breeding occurs mostly in spring, but may occur throughout the year in certain localities (Parera 1996a). Gestation is 56 days (Bertonatti and Parera 1994), and litter size varies from one to five young ones (Bertonatti and Parera 1994), usually two or three (Parera 1996a).

Excessive hunting of L. longicaudis for its pelt in the period 1950-1970 resulted in local extinction over parts of its former range (Brack-Egg 1978; Donadio 1978). Although current hunting and population status are unknown (Emmons 1990), continued illegal hunting (Chehebar 1991), habitat destruction through mining and ranching, and water pollution are likely to be responsible for its rareness (Alho and Lacher 1991; Alho et al. 1998; Chehebar 1990; Gallo 1986; Melendres 1978). Neotropical otters show little fear of humans (Parera 1993), and are sometimes killed incidentally in fishing operations (Dunstone and Strachan 1988) or kept in captivity by fishermen who use trained otters to aid in fishing practices (Parera 1996a).

Lontra longicaudis is listed as endangered in the Appendix I of the Convention on the International Trade of Endangered Species of Wild Fauna and Flora (CITES; Emmons, 1990) and by the Mexican Ministry of Ecology (Ceballos and Navarro 1991). It is also listed as endangered by the United States Department of Interior. The neotropical otter is listed as a priority species by the Fundacion Vida Silvestre Argentina (Bertonetti and Parera 1994). This species is currently protected in Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad, Tobago, Uruguay, and Venezuela (Aranda 1991; Brack-Egg 1978; Chehebar 1990; Mondolfi and Trebbau 1978). Neotropical otters are not legally protected in Guyana and Honduras, and no information is available on the distribution or legal status of neotropical otters in Belize, El Salvador, French Guiana, and Guatemala (Chehebar 1990).

Conservation priorities for the neotropical otter should focus on field surveys of current populations, identification of key habitats, protection of areas where high populations remain, and stricter regulations to prevent release of toxic waste in riverine systems (Mason and Macdonald 1990).

Duplaix, N. 1978. Synopsis of the status and ecology of the giant otter in Suriname. In: N. Duplaix (ed.), Otters: Proceedings of the First Working Meeting of the Otter Specialist Group, pp. 48-54. Morges, Switzerland.

Mondolfi, E. and Trebbau, P. 1978. Otters: Proceedings of the First Working Meeting of the Otter Specialist Group. In: N. Duplaix (ed.), Distribution and status of the giant otter (Pteronura brasiliensis) in VenezuelaOtters. Proceedings of the First Working Meeting of the Otter Specialist Group, pp. 34-42. Morges, Switzerland.